[Tom Line]

You want the two bars nearly as far forward as you can get them. The ball should touch the top one just before the bottom one. The bottom one does not spin. The ball rests on the bottom bar, taking 90% of the normal force. The rest of the normal force is the ball just barely touching the ground. The robot is actually physically carrying the ball, but because the ball doesn't break ground contact it's not a penalty. That how, if you watch 217, 1114, 33, and others, they can whip around, back up, pick balls off the wall, etc because they are quite literally holding the ball.

Watch robowranglers video for a nice closeup of it in action.